1. Field of the Invention
The invention relates to a friction clutch plate, a friction clutch and a driving force transmission apparatus.
2. Description of Related Art
There is a driving force transmission apparatus that includes friction clutch plates each having a plurality of minute grooves open at a sliding surface side in order to improve durability by suppressing abrasion of a contact surface (sliding surface) (for example, Japanese Patent Application Publication No. 2005-36863 (JP 2005-36863 A)).
In such a driving force transmission apparatus, the oil film thickness of lubricant that is interposed between each of the above-described friction clutch plates and an adjacent one of friction clutch plates, which is relatively rotatable with respect to the above-described friction clutch plates, is kept at an appropriate size. Thus, dependence of coefficient of friction μ on a slip velocity v between both friction clutch plates (μ-v characteristic) has a positive gradient (δμ/δv≧0), so it is possible to ensure a favorable driving force transmission characteristic that has excellent judder resistance.